Spectral decomposition for mapping old oil sand channel, Alberta, Canada

Abstract

Decomposing the seismic data into its spectral components can provide vital stratigraphic and structural details that cannot be seen in the broadband data. The technique shows excellent results particularly in tertiary basins such as the Gulf of Mexico and West Africa on which it was first implemented. Therefore many interpreters worried that it would not work well in other environments. Surprisingly, the method showed interesting results in older and less porous rocks with less contrast between shale and sand as well, and in different areas around the world. In this study, spectral decomposition has been performed in order to identify stratigraphic features of Glauconitic oil sand channel of Early Cretaceous age in Alberta, Canada. We selected first a continuous horizon that was close and conforms to the channel interval; we then implemented spectral analyses for the interval that corresponds to the channel location. Short Window Fourier Transform workflow could successfully image the channel's stratigraphic features. Moreover, the producing oil wells in the sand-fill channel were found to be correlating with high amplitude spectrum; while the dry wells in the shale-plugged channel fell in low amplitude anomaly. Furthermore, spectral decomposition could discriminate the regional geology from sand-fill channel in dry wells located in relatively low impedance area where the differentiation using P-impedance was ambiguous.